What's Too Toasty?.

[thejeepdude]

1100 degrees F or the price of a new motor & part? Whats the cheapest insurance!!!!!!!!!!!!!!!!!!!!!!!!

Remember that Cummins' recommendations are based on POST-TURBO pyrometer readings. Make sure you're comparing apples to apples. A completely stock motor can and will run over 1100 (pre-turbo) all day long by design. My stock '05 will reach about 1300-1350 towing through the mountains.

 

[Tinsmith3]

1450

I have pulled my 33' 5th 12,000k on long uphill pulls, at a steady 1450 pre-turbo for 45 minutes without any trouble.

 

[jwilliams3]

I have pulled my 33' 5th 12,000k on long uphill pulls, at a steady 1450 pre-turbo for 45 minutes without any trouble

You should change your username to "Braveheart"



Good testament to what a Cummins can handle!!

 

[Forrest Nearing]

Talked to a Cummins Rep and he indicated no more than 1100 degrees F. aluminum begins to melt @ 1200 Degress F. Just food for thought

I'd talk to a different Cummins rep because that guy doesn't know what he's talking about...



if a bone stock truck will do 1400+ on a long grade, why would you have to keep it under 1100?



just because EGT's are at 1400, it doesn't mean that piston crown temps are at 1200*

 

[betterthanstock]

Ice melts at 32 F, and aluminum at 1250. It takes a while for a cube to melt, and so it does for your piston. How long do you plan on keeping it?

 

[TSpecht]

It also fails to take into account the cooling nozzles and passages in and around the pistons and assembly. That is part of the reason it can withstand somewhat higher temperatures than the melting point of aluminum. Interestingly enough ice melts at 32° but that is also where it freezes, same with Al. Ever put a cup full of water directly on a campfire? Interestingly enough the cup won't burn or melt so long as there's water there. May not have too much to do with the discussion but I like campfires...

 

[Prairie Dog]

I too tried to find a "red line" EGT. Never got any hard numbers, just advice to "keep er under 1300" When I asked how folks arrived at that number no one could give me any answers. I also contacted cummins and they could not give me an answer either. I guess when you start melting things you know you've been running too hot.

Originally 1300 was selected because the alluminum pistons supposedly melt at 1290 but since then I've heard many folks sustain much higher temps. One person wrote that Cummins runs them at 1500 for 30 minutes during testing with no damage.

 

[betterthanstock]

It also fails to take into account the cooling nozzles and passages in and around the pistons and assembly. That is part of the reason it can withstand somewhat higher temperatures than the melting point of aluminum. Interestingly enough ice melts at 32° but that is also where it freezes, same with Al. .

Ok, but the actual flame during combustion can reach 3000 deg, so the exhaust gas is just what's left once the fire is out. Also, cool air comes in immediately thru the intake valve, so again, does anybody know the actual temperature of the face of the piston? Cummins does for their stock timing/fuel/boost, but once you start changing things, the only real way to know is when you melt it down.



Measure the time above 1200 in seconds, not minutes, and you'll be ok.



Also, the oil on cylinders can burn, causing scoring if it's too hot.